There are various well-known electronic display means enabling someone holding a stylus to ‘draw’ or ‘write’ on said display means, and to see what they have drawn appear on, for example, a colour LCD screen.
To accomplish the above, it is also known that a suitable electrical charge at an electrode adjacent to an oil droplet, where said droplet is located within a suitable electrolyte, and where said droplet is separated from said electrode by a hydrophobic polymer layer, can induce a change in the shape of an oil droplet, thus changing the colour of a pixel on a screen.
It is similarly known that, in a similar system, a polar liquid droplet may replace an oil droplet. The polar liquid droplet may be moved when arranged with an insulating liquid surrounding it, with a ground plane within proximity to the droplet/insulating liquid reservoir, and with a hydrophobic polymer insulating layer located in between the droplet and more than one separately-addressable adjacent electrodes. This can be accomplished by charging, one by one, a number of electrodes adjacent to said droplet so as to cause the hydrophobic property of the local polymer surface to become hydrophilic, and causing the droplet to be attracted successively to first one and then another charged electrode-proximate location. Arrangements for achieving these effects are described in existing prior art.
To date, however, there are few if any colour display means which are electronically ‘writeable’ with a stylus, as well as being electronically ‘erasable’, and which are low-cost to manufacture.
Therefore, there is a need for a low-cost electronic display means which can display in colour what is drawn or written on its display area, and can later electronically erase the same displayed items. Further, there is a need for low-cost colour display means which do not employ, or which do not require, a stylus to achieve satisfactory addressing. The purpose of some of the following inventions is to exploit such approaches for a new application, that of directing light onto, or through, differently-coloured light filters so as to provide various different and innovative display means.